CTLA4 and chronic myelogenous leukemia, BCR-ABL1 positive: Another prospective phase 1 clinical trial (NCT01822509) is presently evaluating the safety and immunologic activity of ipilimumab (161) (CTLA-4 blockade) or nivolumab (162) (PD-1 blockade) for relapsed hematologic malignancies including CML after allo-HSCT.